Cytotoxic platinum complex, its preparation and therapeutic use

ABSTRACT

Platinum(IV) complexes especially suitable for antitumor therapy and methods for their preparation. Further provided is a method for treating a subject, in particular a human, suffering from a disease including administering a platinum(IV) complex of the present invention, which disease is especially preferably but not exclusively a cancer. Further provided is a method of inhibiting the growth of tumor cells by contacting the cells with a platinum(IV) complex of the present invention and a pharmaceutical composition including a platinum(IV) complex of the present invention. The platinum(IV) complexes of the present invention represent a novel class of platinum anticancer prodrugs for the treatment of diseases especially of cancer. The platinum(IV) complexes of the present invention exhibit advantageously high cytotoxic activity in various cancer types superior to commonly used platinum-based complexes. In addition, the complexes proved to be highly effective even against cisplatin-resistant cancers.

TECHNICAL FIELD

The present invention relates to a novel platinum(IV) complex especiallysuitable for antitumor therapy and a method for preparing it. Furtherprovided is a method for treating a subject, in particular a human,suffering from a disease comprising administering the platinum(IV)complex of the present invention. Said disease is especially preferablybut not exclusively a cancer. Further provided is a method of inhibitingthe growth of tumor cells by contacting the cells with the platinum(IV)complex of the present invention and a pharmaceutical compositioncomprising said platinum complex.

BACKGROUND OF THE INVENTION

Cancer remains a life-threatening disease affecting a steadilyincreasing number of people overall in the world. Platinum-basedchemotherapeutic compounds, including cisplatin, carboplatin andoxaliplatin, have been widely applied for the treatment of differenttypes of cancer in clinical trials for decades. These platinum complexesreact in vivo, and they are proposed to bind to DNA and subsequently tocause crosslinking of DNA, which ultimately triggers apoptosis.

Although over 50% of cancer patients have been treated withplatinum-based chemotherapeutic compounds, these compounds areassociated with severe side effects. In addition, both intrinsic andacquired resistances against these compounds have been observed afterthe treatment with these compounds which further significantly limitstheir clinical use.

Thus, there remains a strong need for new and effective compoundssuitable for treating cancer with acceptable side effects that can beused either as alternatives or alternatively in addition to commonchemotherapeutic compounds such as cisplatin or other anticancertherapies such as radiotherapy and which are effective even if thecancer is or has developed chemoresistance against commonly usedchemotherapeutic compounds such as cisplatin.

SUMMARY OF THE INVENTION

The first aspect of the present invention relates to a platinum(IV)complex. Said platinum complex comprises a structure of Formula (I):

X, X′, Y, Y′ and Z are independently selected from an electron donorligand and may be linked to each other in any combination.

n is selected from zero, any positive charge or any negative charge.

R is an aryl-comprising moiety selected from the group consisting of:

with L and L′ being a linker group, W being a linker atom, W′ being anatom or group which can be attached by a double bond and R₁ to R₉ beingindependently selected from a substituent or a hydrogen atom.

as used in this invention means a double bond and indicates that theconfiguration might be the (E) and (Z) configuration, i.e. it covers the(E) and the (Z) configuration.

The platinum(IV) complex of the present invention comprises a structureof Formula (I) with the provision that the platinum complex is notchalcoplatin.

Further provided with the present invention is a method for preparingthe platinum(IV) complex described above, i.e. for preparing a platinumcomplex comprising a structure of Formula (I):

with X, X′, Y, Y′, Z, n and R as defined above.

Said method comprises linking a platinum complex precursor comprising astructure of Formula (XI):

which is in particular a platinum(IV) complex precursor with anaryl-comprising moiety R to form the platinum(IV) complex as describedabove, wherein X, X′, Y, Y′ and Z are as defined above, n′ means zero orany positive or negative charge and wherein R is an aryl-comprisingmoiety selected from one of:

with L, L′, W, W′ and R₁ to R₉ as defined above.

The present invention in a third aspect refers to a method for treatinga subject such as a human suffering from a disease such as a tumor, inparticular a cancer, comprising administering an effective amount of aplatinum(IV) complex as described above to said subject, i.e. comprisingadministering a platinum(IV) complex comprising a structure of Formula(I) to said subject:

with X, X′, Y, Y′, Z, n and R as defined above and with the provisionthat the platinum complex is not chalcoplatin.

The present invention further provides a pharmaceutical compositioncomprising:

(i) a platinum(IV) complex as described above; and

(ii) a pharmaceutically tolerable excipient such as selected from apharmaceutically tolerable carrier, salt, buffer, water, diluent, afiller, a binder, a disintegrant, a lubricant, a coloring agent, asurfactant or a preservative or a combination thereof.

According to the invention is also the platinum(IV) complex describedabove for use as a medicament for the treatment of cancer. Theplatinum(IV) complex can be used in an effective amount for treating aliving organism like an animal or a human, in particular a mammal,preferably a human. Another aspect of the invention refers to the use ofthe platinum(IV) complex described above for preparing a medicament fortreatment of cancer. The platinum(IV) complex described above may beused in monotherapy or in combination with at least a furtherchemotherapeutic compound.

In another aspect, the invention provides a method of inhibiting thegrowth of tumor cells. Said method comprises the step of contacting apopulation of tumor cells such as a population of cancer cells with theplatinum(IV) complex described above. In particular, the cell growth isreduced and/or cell death is induced.

The platinum(IV) complex of the present invention represents a novelclass of platinum anticancer prodrugs for the treatment of diseasesespecially cancer. In particular, the inventors could show that theplatinum(IV) complexes of the present invention can have advantageouslyhigh cytotoxic activity against cancer cells, with the platinum(IV)complex of Formula (IIa) being among the most active platinum(IV)prodrugs known so far. For example, the inventor found that saidplatinum(IV) complex is significantly more active than both cisplatinand chalcoplatin, and the IC₅₀ values of said complex are in thenanomolar range in cells from several cancer types. In addition, thecomplexes proved to be highly effective against cisplatin-resistantcancer cells. For example, the platinum(IV) complex of Formula (IIa)proved to be able to overcome cisplatin resistance with reducedResistant Factors compared to cisplatin.

Therefore, compared with the existing and commonly used platinum-basedchemotherapeutic compound cisplatin, the platinum(IV) complexes of thepresent invention have the advantage of superior effectiveness,especially against cisplatin-resistant cancer cells and, thus, representa highly promising treatment option such as for cancer therapy.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. The invention includes all such variations andmodifications. The invention also includes all steps and featuresreferred to or indicated in the specification, individually orcollectively, and any and all combinations of the steps or features.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 summarizes the synthesis route of monochalcoPt(IV);

FIG. 2 summarizes the synthesis route of dichalco-oxaliPt(IV);

FIG. 3 summarizes the synthesis route of mono4FP-Pt(IV);

FIG. 4 summarizes the synthesis route of di4FP-Pt(IV); and

FIG. 5 summarizes the synthesis route of mono4FP-oxaliPt(IV).

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise defined, all technical terms used herein have the samemeaning as commonly understood by one skilled in the art to which theinvention belongs.

As used herein, “comprising” means including the following elements butnot excluding others. “Essentially consisting of” means that thematerial consists of the respective element along with usually andunavoidable impurities such as side products and components usuallyresulting from the respective preparation or method for obtaining thematerial such as traces of further components or solvents. “Consistingof” means that the material solely consists of, i.e. is formed by therespective element. As used herein, the forms “a,” “an,” and “the,” areintended to include the singular and plural forms unless the contextclearly indicates otherwise.

Other than in the working examples, or where otherwise indicated, allnumbers used herein should be understood as modified in all instances bythe term “about” The term “about” when used in connection with a numbercan mean, for example, ±2%.

Moreover, the words “example” or “exemplary” used in this invention areintended to serve as an example, instance, or illustration. Any aspector design described in this disclosure as “exemplary” is not necessarilyto be construed as preferred or advantageous over other aspects ordesigns. Rather, use of the words “example” or “exemplary” is intendedto present concepts in a concrete fashion. As used in this application,the term “or” is intended to mean an inclusive “or” rather than anexclusive “or”. That is, unless specified otherwise, or clear fromcontext, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A; X employs B; or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances.

The present invention provides a platinum(IV) complex. Said platinum(IV)complex comprises a structure of Formula (I):

Where X, X′, Y, Y′ and Z are independently selected from an electrondonor ligand and may be linked to each other in any combination.

n is selected from zero, any positive charge or any negative charge.

R is an aryl-comprising moiety selected from the group consisting of:

with L and L′ being a linker group, W being a linker atom, W′ being anatom or group which can be attached by a double bond, R₁ to R₉ beingindependently selected from a substituent or a hydrogen atom, and

is a double bond covering the (E) and (Z) configuration.

The platinum(IV) complex of the present invention comprises a structureof Formula (I) with the provision that the platinum complex is notchalcoplatin, i.e. with the proviso that the platinum(IV) complex doesnot have the following structure:

I.e. with the proviso that when R is

and either the ligands Y and Y′ are ammine (NH₃, i.e. amine (NH₃) asligand) each and X and X′ are chlorido each or if Y and Y′ are chloridoeach and X and X′ are ammine (NH₃) each, Z is not —OR.

Said platinum(IV) complex can be present in form of a salt, i.e.suitable counterions may be present or in form of a solvate. Acounterion might affect the solubility or other chemical or physicalproperties of the platinum(IV) complex, wherein the exact nature of thecounterion is not critical. The counterion is preferablypharmaceutically acceptable, i.e. not with therapeutically relevanttoxicity in the amounts used. Counterions can in particular be anionswhich are unlikely to bind directly to the platinum center, i.e.non-coordinating anions. As used herein, the term “solvate” refers to acomplex of variable stoichiometry formed by a solute, i.e. theplatinum(IV) complex, and a solvent. If the solvent is water, thesolvate formed is a hydrate.

The platinum in the platinum complex of the present invention is in theoxidation state (IV), i.e. the platinum complex of the present inventionis a platinum(IV) complex.

R is an aryl-comprising moiety. The term “aryl” as used herein, refersto an aromatic monocyclic ring system having 6 ring atoms, of which allthe ring atoms are carbon, and which ring may be substituted with R₁ toR₉. R comprises one or two aryl rings. Said part of R is also referencedas the “aromatic part”. “Aromatic” means the presence of a delocalized,conjugated π-electron system.

R further comprises a linker atom W which is an atom directly attachedto an aryl and can include, but is not limited to, a heteroatom such asoxygen (O) or sulfur (S). In particular embodiments of the presentinvention, W is an oxygen atom.

W′ can be any atom or a group which can be attached by a double bondprovided that this results in the formation of a stable moiety,including, but not limited to, a heteroatom such as an oxygen atom, asulfur atom or a nitrogen (N) atom or a heteroatom-containing group. Inparticular embodiments of the present invention, W′ is an oxygen atom ora sulfur atom, in particular W′ is an oxygen atom.

The linker group L is an organic unit of any lengths comprising atoms orgroups to link, i.e. to connect, two parts of the platinum complex ofthe present invention, namely the ‘platinum part’ of the platinumcomplex and the ‘aromatic part’ of R together, it thus links theplatinum part with the W-aromatic part of R. Not limiting examplesinclude a straight chain or branched alkanediyl or alkenediyl chain. Inparticular embodiments of the present invention, L is —(CH₂)_(m)—,wherein m is an integer which is >0 for example m is 1, 2, 3 or 4, mostpreferably L is —CH₂—, i.e. a methanediyl group.

The linker group L′ is an organic unit of any lengths comprising atomsor groups to link, i.e. to connect, the two oxygen atoms together. L′can be, for example, a straight chain or branched alkanediyl oralkenediyl chain or a carbon-oxygen chain. In particular embodiments ofthe present invention, L′ is —(CH₂)_(m′)—i.e. a methanediyl group and m′is an integer and >0 such as 1, 2 or 3, in particular m′ is 1.

R₁ to R₉ are substituents which can be, for example, but not limited to,a nitrogen-containing group, an oxygen-containing group, aphosphorous(P)-containing group, a sulfur-containing group, alkylgroups, a halogen atom or a hydrogen atom or the like. R₁ to R₉ are inparticular embodiments of the present invention selected from a hydrogenatom or a halogen atom, more preferably from a hydrogen atom or achlorine atom.

An electron donor ligand means a ligand which is electron donating, i.e.has a donor atom with electron-donating ability such as a nitrogen atom,an oxygen atom, a phosphorous (P) atom or a sulfur atom. Non-limitingexamples of electron donor ligands are nitrogen-containing ligands,oxygen-containing ligands, phosphorous-containing ligands,sulfur-containing ligands and halogen containing ligands. Electron donorligands can, for example, include, imine, aqua, halido (i.e. halide ionsin particular including chlorido, bromido or fluorido), amines,diamines, triamines, ammine (NH₃), alkyl, cyanido, nitrato, hydroxido,alkoxy, phenoxy, anions of an alkyl mono- or poly-, such as di-,carboxylic acid such as oxalato or dianions of glycolic acid, analcoholato ligand, alkylthio, thiolato, phosphito, phosphane,β-diketone, nitrato, a heterocycle such as pyridine or 2-methylpyridineor it can be —OR with R being an aryl-comprising moiety as definedabove. The term “alkyl” as used herein refers to saturated,straight-chain or branched hydrocarbons which may, for example, containbetween 1 and 20 carbon atoms such as 1 to 5 carbon atoms. The electrondonor ligands in particular include ammine (NH₃), aqua, halido such aschlorido, hydroxido, oxalato, diamines such as 1,2-cyclohexanediamine or—OR with R being an aryl-comprising moiety as defined above. Y, Y′, X,X′ and Z may optionally be linked to each other in any combination toform polydentate ligands, in particular bidentate ligands. In particularembodiments, X and X′ are linked to each other to form a bidentateligand and/or Y and Y′ are linked to each other to form a bidentateligand.

In particular embodiments of the present invention, X, X′, Y and Y′ areindependently selected from ammine (NH₃), aqua, halido such as chlorido,hydroxido, oxalato or diamines such as 1,2-cyclohexanediamine, inparticular from ammine (NH₃), chlorido, hydroxido, oxalato or1,2-cyclohexanediamine and Z is selected from ammine (NH₃), aqua, halidosuch as chlorido, hydroxido, oxalato or diamines such as1,2-cyclohexanediamine or —OR with R being an aryl-comprising moiety asdefined above, in particular Z is selected from ammine (NH₃), chlorido,hydroxido, oxalato, 1,2-cyclohexanediamine or —OR.1,2-cyclohexanediamine means in particulartrans-(1R,2R)-1,2-cyclohexanediamine.

n is zero or any positive or any negative charge. In embodiments of thepresent invention n is zero, i.e. the platinum complex is in particulara neutral platinum complex.

I.e., the platinum(IV) complex of the present invention comprises astructure selected from one of Formulas (II) to (X):

wherein X, X′, Y, Y′, Z, L, L′, W, W′, n and R₁ to R₉ are as definedabove.

In a preferred embodiment of the present invention, the platinum(IV)complex comprises a structure selected from Formula (II) or (III):

wherein X, X′, Y, Y′, Z, L, W, W′, n and R₁ to R₉ are as defined above.

In particular embodiments of the present invention, the platinum(IV)complex comprises a structure of Formula (II):

wherein X, X′, Y, Y′, Z, L, W, n and R₁ to R₉ are as defined above.Preferably, X, X′, Y and Y′ are independently selected from ammine(NH₃), aqua, halido, hydroxido, oxalato or diamines and Z is selectedfrom ammine (NH₃), aqua, halido, hydroxido, oxalato or diamines or —ORwith R being an aryl-comprising moiety as defined above. Furtherpreferred, X, X′, Y and Y′ are independently selected from ammine (NH₃),oxalato, 1,2-cyclohexanediamine and a halido and Z is selected fromhydroxido or —OR with R being an aryl-comprising moiety as describedabove, in particular R is:

with L, W and R₁ to R₉ as described within this embodiment, i.e. R inFormula (II) most preferably corresponds to the R in —OR of Z.

L is preferably —(CH₂)_(m)—, wherein m is an integer selected from 1, 2,3 or 4, more preferably m is 1. W is preferably selected from an oxygenatom or a sulfur atom, more preferably W is an oxygen atom. R₁ to R₉ arepreferably independently selected from a hydrogen atom or a halogenatom, more preferably R₁ to R₄ are hydrogen atoms and R₅ to R₉ areindependently selected from a hydrogen atom or a halogen atom with mostpreferably R₇ and R₈ being a chloride atom each and R₅, R₆ and R₉ beinga hydrogen atom each.

Most preferably, the platinum(IV) complex in such embodiments comprisesa structure of Formula (IIa) or (IIb) and in particular essentiallyconsists of a compound of Formula (IIa) or (IIb):

In alternative preferred embodiments of the present invention, theplatinum(IV) complex comprises a structure of Formula (III):

wherein X, X′, Y, Y′, Z, L, W, W′, n and R₁ to R₅ are as defined above.Preferably, X, X′, Y and Y′ are independently selected from ammine(NH₃), aqua, halido, hydroxido, oxalato or diamines and Z is selectedfrom ammine (NH₃), aqua, halido, hydroxido, oxalato or diamines such as1,2-cyclohexanediamine or —OR with R being an aryl-comprising moiety asdescribed above. Further preferred, X, X′, Y and Y′ are independentlyselected from ammine (NH₃), a halido, oxalato and 1,2-cyclohexanediamineand Z is selected from hydroxido or —OR with R being an aryl-comprisingmoiety as described above, in particular R is:

with L, W, W and R₁ to R₅ as described within this embodiment, i.e. R inFormula (III) most preferably corresponds to the R in —OR of Z.

L is preferably —(CH₂)_(m)—, wherein m is an integer selected from 1, 2,3 or 4, more preferably m is 1. W is preferably selected from an oxygenatom or a sulfur atom, more preferably W is an oxygen atom. W′ ispreferably an oxygen atom. R₁ to R₄ are preferably independentlyselected from a hydrogen atom or a halogen atom and R₅ is a hydrogenatom, more preferably all of R₁ to R₅ are hydrogen atoms.

Most preferably, the platinum complex in such embodiments comprises astructure of Formula (IIIa), (IIIb) or (IIIc) and in particularessentially consists of a compound of Formula (IIIa), (IIIb) or (IIIc):

Further provided with the present invention is a method for preparingthe platinum(IV) complex described above, i.e. for preparing aplatinum(IV) complex comprising a structure of Formula (I):

with X, X′, Y, Y′ and Z, n and R as defined above.

Said method comprises linking a platinum complex precursor which is inparticular a platinum(IV) complex precursor and which comprises astructure of Formula (XI):

with an aryl-comprising moiety R to form the platinum(IV) complex asdescribed above, wherein X, X′, Y, Y′ and Z are as defined above, n′means zero or any positive or negative charge and wherein R is selectedfrom one of:

wherein L, L′, W, W′ and R₁ to R₉ are as defined above.

The platinum complex precursor in particular platinum(IV) complexprecursor can comprise a structure of Formula (XIa):

i.e. Z is hydroxido. Particular platinum complex precursors comprise astructure of Formula (XIb) or (XIc) given further below and are inparticular platinum(IV) precursor complexes, i.e. most preferably theplatinum complex precursor is a platinum(IV) complex precursor selectedfrom a structure of Formula (XIb) or (XIc) given further below. Themethod is preferably carried out under inert atmosphere such as underargon.

In an embodiment of the present invention, the method is for preparing aplatinum(IV) complex comprising a structure of Formula (II) such as ofFormula (IIa) or (IIb) comprising linking a platinum complex precursorof Formula (XI) such as of Formula (XIa) with an aryl-comprising moietywhich is

which method comprises steps of:

(i) optionally preparing a hydroxysuccinimide(NHS)-ester of Formula(XII) such as of Formula (XIIa);

(ii) reacting a platinum complex precursor of Formula (XI) such as ofFormula (XIa) with the N-hydroxysuccinimide(NHS)-ester of Formula (XII)such as of Formula (XIIa):

with L, W and R₁ to R₉ as defined above, such as

(iii) isolating the platinum(IV) complex of Formula (II) such as ofFormula (IIa) or (IIb).

Step (ii) in particular comprises:

a) preparing a mixture of the platinum complex precursor and theNHS-ester in a reaction solvent;

b) stirring the mixture after step a) for at least about 8 h at atemperature of at least about 20° C.

“Isolating” the platinum(IV) complex means at least partially separatingthe platinum(IV) complex from other components such as side products,the reactants and the solvent present in the reaction mixture after step(ii). Step (iii) in particular comprises filtering the mixture forobtaining a filtrate, adding a precipitation solvent to the filtrate forobtaining a precipitate and washing the precipitate with a washingsolvent.

The reaction solvent in step a) is preferably dimethyl sulfoxide (DMSO).In particular, the NHS-ester is added in step a) in form of a mixturewith at least a part of the reaction solvent, in particular DMSO. Theprecipitation solvent can be a halogenated hydrocarbon and/or a dialkylether, in particular dichloromethane, diethyl ether or a mixture ofboth. The washing solvent can be a halogenated hydrocarbon, inparticular dichloromethane.

In another embodiment of the method of the present invention, the methodis for preparing a platinum(IV) complex comprising a structure ofFormula (III) such as of Formula (IIIa), (IIIb) or (IIIc) comprisinglinking a platinum complex precursor of Formula (XI) such as of Formula(XIa) with an aryl-comprising moiety which is

which method comprises steps of:

(i) optionally preparing a hydroxysuccinimide(NHS)-ester of Formula(XIII) such as of Formula (XIIIa);

(ii) reacting a platinum complex precursor of Formula (XI) such as ofFormula (XIa) with the NHS-ester of Formula (XIII) such as of Formula(XIIIa):

with L, W, W′ and R₁ to R₅ as defined above, such as

and

(iii) isolating the platinum(IV) complex of Formula (III) such as ofFormula (IIIa), (IIIb) or (IIIc).

Step (ii) in particular comprises:

a) preparing a mixture of the platinum complex precursor and theNHS-ester in a reaction solvent;

b) stirring the mixture after step a) for at least about 8 h at atemperature of at least about 20° C.

Step (iii) in particular comprises filtering the mixture for obtaining afiltrate, adding a precipitation solvent to the filtrate for obtaining aprecipitate and washing the precipitate with a washing solvent.

The reaction solvent in step a) is preferably dimethyl sulfoxide (DMSO).In particular, the NHS-ester is added in step a) in form of a mixturewith at least a part of the reaction solvent, in particular DMSO. Theprecipitation solvent can be a halogenated hydrocarbon and/or a dialkylether, in particular dichloromethane, diethyl ether or a mixture ofboth. The washing solvent can be a halogenated hydrocarbon, inparticular dichloromethane.

The methods may optionally comprise the step (i) of preparing theNHS-ester. The NHS-ester of Formula (XII) such as of Formula (XIIa) orof Formula (XIII) such as of Formula (XIIIa) may be prepared comprisingsteps of:

a) providing a mixture of a compound of Formula (XIV) such as (XIVa) or(XV) such as (XVa) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC) and N-hydroxysuccinimide (NHS):

with L, W, W′ and R₁ to R₉ as defined above;

b) isolating the NHS-ester.

Step a) is preferably carried out by stirring the mixture in a reactionsolvent at a temperature between about 20° C. and about 30° C., such asat about 25±2° C., for at least about 8 h, in particular for at leastabout 10 h. The reaction solvent in this step a) is preferably anorganic nitrile, in particular acetonitrile.

“Isolating” the NHS-ester in step b) means at least partially separatingthe NHS-ester from other components such as side products, the reactantsand the solvent present in the reaction mixture after step a). Step b)in particular comprises filtering the mixture for obtaining a residueand washing the residue with water and optionally freeze-drying theresidue.

In a particular embodiment, the method is for preparing a platinumcomplex of Formula (IIa) and the method comprises steps of:

(i) optionally preparing an N-hydroxysuccinimide(NHS)-ester of Formula(XIIa):

comprising:

a) providing a mixture of a compound of Formula (XIVa) and1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) andN-hydroxysuccinimide (NHS):

and stirring the mixture in a reaction solvent such as acetonitrile at atemperature between about 20° C. and about 30° C., such as at about25±2° C., for at least about 8 h, in particular for at least about 10 h;

b) isolating the NHS-ester in particular comprising filtering themixture for obtaining a residue and washing the residue with water andoptionally freeze-drying the residue;

(ii) reacting a platinum complex precursor of Formula (XIb):

with the N-hydroxysuccinimide(NHS)-ester of Formula (XIIa) comprising:

a) suspending the platinum complex precursor in a reaction solvent whichis preferably DMSO and adding the NHS-ester in particular in reactionsolvent, in particular under stirring, wherein the molar ratio of theplatinum complex precursor and NHS-ester is between about 0.6:1 andabout 2:1, in particular the molar ratio is about 1:1;

b) stirring the mixture after step a) for at least about 8 h, inparticular for at least about 24 h and further preferred for at leastabout 72 h at a temperature between about 20° C. and about 30° C., suchas at about 25±2° C.;

(iii) isolating the platinum(IV) complex of Formula (IIa) comprisingfiltering the mixture after step b) for obtaining a filtrate, adding aprecipitation solvent which is in particular dichloromethane to thefiltrate and after about 24 h, in particular after about 48 h washingthe residue with a washing solvent which is in particulardichloromethane.

In another particular embodiment, the method is for preparing aplatinum(IV) complex of Formula (IIb) and the method comprises steps of:

(i) optionally preparing an N-hydroxysuccinimide(NHS)-ester of Formula(XIIa):

comprising:

a) providing a mixture of a compound of Formula (XIVa) and1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) andN-hydroxysuccinimide (NHS):

and stirring the mixture in a reaction solvent such as acetonitrile at atemperature between about 20° C. and about 30° C., such as at about25±2° C., for at least about 8 h, in particular for at least about 10 h;

b) isolating the NHS-ester in particular comprising filtering themixture for obtaining a residue and washing the residue with water andoptionally freeze-drying the residue;

(ii) reacting a platinum complex precursor of Formula (XIc):

with an N-hydroxysuccinimide(NHS)-ester of Formula (XIIa) comprising:

a) suspending the platinum complex precursor and the NHS-ester in areaction solvent which is preferably DMSO, wherein the molar ratio ofthe platinum complex precursor and the NHS-ester is between about 1:15and about 1:5, in particular the molar ratio is about 1:10;

b) stirring the mixture after step a) for at least about 8 h, inparticular for at least about 12 h such as for at least about 24 h at atemperature of at least 60° C. and in particular of between about 75° C.and about 85° C.;

(iii) isolating the platinum(IV) complex of Formula (IIb) comprisingfiltering the mixture after step b) for obtaining a filtrate, adding aprecipitation solvent which is in particular a mixture ofdichloromethane and diethyl ether to the filtrate and after about 24 h,in particular after about 48 h washing the residue with a washingsolvent which is in particular dichloromethane.

In a further particular embodiment, the method is for preparing aplatinum(IV) complex of Formula (IIIa) and the method comprises stepsof:

(i) optionally preparing an N-hydroxysuccinimide(NHS)-ester of Formula(XIIIa):

comprising:

a) providing a mixture of a compound of Formula (XVa) and1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) andN-hydroxysuccinimide (NHS):

and stirring the mixture in a reaction solvent such as acetonitrile at atemperature between about 20° C. and about 30° C., such as at about25±2° C., for at least about 8 h, in particular for at least about 10 h;

b) isolating the NHS-ester in particular comprising filtering themixture for obtaining a residue and washing the residue with water andoptionally freeze-drying the residue;

(ii) reacting a platinum complex precursor of Formula (XIb):

with an N-hydroxysuccinimide(NHS)-ester of Formula (XIIIa):

comprising

a) suspending the platinum complex precursor in a reaction solvent whichis preferably DMSO and adding the NHS-ester in particular in reactionsolvent, in particular under stirring, wherein the molar ratio of theplatinum complex precursor and the NHS-ester is between about 0.6:1 andabout 2:1, in particular the molar ratio is about 1:1;

b) stirring the mixture after step a) for at least about 8 h, inparticular for at least about 24 h and further preferred for at leastabout 72 h at a temperature between about 20° C. and about 30° C., suchas at about 25±2° C.;

(iii) isolating the platinum(IV) complex of Formula (IIIa) comprisingfiltering the mixture after step b) for obtaining a filtrate, adding aprecipitation solvent which is in particular a mixture ofdichloromethane and diethyl ether to the filtrate and after about 24 h,in particular after about 48 h washing the residue with a washingsolvent which is in particular dichloromethane.

In a further particular embodiment, the method is for preparing aplatinum(IV) complex of Formula (IIIb) and the method comprises stepsof:

(i) optionally preparing an N-hydroxysuccinimide(NHS)-ester of Formula(XIIIa):

comprising:

a) providing a mixture of a compound of Formula (XVa) and1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) andN-hydroxysuccinimide (NHS):

and stirring the mixture in a reaction solvent such as acetonitrile at atemperature between about 20° C. and about 30° C., such as at about25±2° C., for at least about 8 h, in particular for at least about 10 h;

b) isolating the NHS-ester in particular comprising filtering themixture for obtaining a residue and washing the residue with water andoptionally freeze-drying the residue;

(ii) reacting a platinum complex precursor of Formula (XIb):

with an N-hydroxysuccinimide(NHS)-ester of Formula (XIIIa) comprising:

a) suspending the platinum complex precursor and the NHS-ester in areaction solvent which is preferably DMSO, wherein the molar ratio ofthe platinum complex precursor and NHS-ester is between about 1:15 andabout 1:5, in particular the molar ratio is about 1:10;

b) stirring the mixture after step a) for at least about 8 h, inparticular for at least about 12 h such as for at least about 24 h at atemperature of at least 60° C. and in particular of between about 75° C.and about 85° C.;

(iii) isolating the platinum(IV) complex of Formula (IIIb) comprisingfiltering the mixture after step b) for obtaining a filtrate, adding aprecipitation solvent which is in particular a mixture ofdichloromethane and diethyl ether to the filtrate and after about 24 h,in particular after about 48 h washing the residue with a washingsolvent which is in particular dichloromethane.

In a further particular embodiment, the method is for preparing aplatinum(IV) complex of Formula (IIIc) and the method comprises stepsof:

(i) optionally preparing an N-hydroxysuccinimide(NHS)-ester of Formula(XIIIa):

comprising:

a) providing a mixture of a compound of Formula (XVa) and1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) andN-hydroxysuccinimide (NHS):

and stirring the mixture in a reaction solvent such as acetonitrile at atemperature between about 20° C. and about 30° C., such as at about25±2° C., for at least about 8 h, in particular for at least about 10 h;

b) isolating the NHS-ester in particular comprising filtering themixture for obtaining a residue and washing the residue with water andoptionally freeze-drying the residue;

(ii) reacting a platinum complex precursor of Formula (XIc):

with an N-hydroxysuccinimide(NHS)-ester of Formula (XIIIa) comprising:

a) suspending the platinum complex precursor in a reaction solvent whichis preferably DMSO and adding the NHS-ester in particular in thereaction solvent, in particular under stirring, wherein the molar ratioof the platinum complex precursor and NHS-ester is between about 0.6:1and about 2:1, in particular the molar ratio is about 1:1;

b) stirring the mixture after step a) for at least about 8 h, inparticular for at least about 24 h and further preferred for at leastabout 72 h at a temperature between about 20° C. and about 30° C., suchas at about 25±2° C.;

(iii) isolating the platinum(IV) complex of Formula (IIIc) comprisingfiltering the mixture after step b) for obtaining a filtrate, adding aprecipitation solvent which is in particular a mixture ofdichloromethane and diethyl ether to the filtrate and after about 24 h,in particular after about 48 h washing the residue with a washingsolvent which is in particular dichloromethane.

The present invention in a third aspect refers to a method for treatinga subject suffering from a disease comprising administering an effectiveamount of a platinum complex as described above to said subject, i.e.comprising administering a platinum(IV) complex comprising a structureof Formula (I) to said subject:

with X, X′, Y, Y′ and Z, n and R as defined above and with the provisionthat the platinum complex is not chalcoplatin, i.e. with the provisothat the platinum complex does not have the following structure:

This means a proviso that when R is

and either the ligands Y and Y′ are ammine (NH₃) each and X and X′ arechlorido each or if Y and Y′ are chlorido each and X and X′ are ammine(NH₃) each, Z is not —OR.

The disease is in particular a tumor and in particular a cancer, forexample, but not limited to one of:

-   -   an ovarian cancer,    -   a lung cancer,    -   a breast cancer, or    -   a colorectal cancer.

The term “tumor” simply refers to all neoplastic cell growth andproliferation being of benign (generally harmless) or malignant(cancerous) growth, and all pre-cancerous and cancerous cells andtissues. The terms “cancer” and “cancerous” describe a physiologicalcondition in subjects in which a population of cells are characterizedby unregulated malignant (cancerous) cell growth.

The cancer can be a cancer which has a natural, i.e. intrinsic, oracquired resistance against one or more chemotherapeutic compounds inparticular which has a natural or has an acquired, i.e. developedresistance against known coordination complexes of platinum such ascisplatin. A cancer is resistant against one or more chemotherapeuticcompounds if it comprises cancer cells which are resistant against saidchemotherapeutic compounds. Accordingly, the cancer cells with aresistant phenotype will be less sensitive or more tolerant to the oneor more chemotherapeutic compounds. Such cancer or cancer cells can bedetected in a subject, cancer or tissue by administering to the subject,tissue, or cell, the one or more chemotherapeutic compounds anddetermining the activity of the chemotherapeutic compounds such as theinduction of cell death or the inhibition of the proliferation of cancercells compared to a reference control, namely cells or tissue of thesame cell or tissue type, a cancer or a subject that do not have theresistance against the chemotherapeutic compound or non-cancerous cells.This can be determined, for example, by means of an MTT assay. A canceror cancer cells which have a natural (intrinsic) or acquired resistanceagainst cisplatin are referenced herein as “cisplatin-resistant”.

In particular embodiments of the present invention, the cancer has anatural or an acquired resistance against cisplatin, also known as cDDP(cis-diamminedichloroplatinum).

The term “subject” used herein refers to a living organism and caninclude but is not limited to a human, a plant and an animal. Thesubject is preferably a human or an animal, in particular the subject isa mammal, preferably a human. The subject is preferably a human having acancer.

The platinum(IV) complex administered, thus, comprises a structureselected from one of Formulas (II) to (X):

wherein X, X′, Y, Y′, Z, L, L′, W, W′, n and R₁ to R₉ are as definedabove.

In particular, the platinum(IV) complex administered can comprise astructure selected from:

Most preferably, the platinum(IV) complex comprises a structure ofFormula (II), in particular of Formula (IIa):

The platinum(IV) complex can be, for example, present in form of apharmaceutically acceptable salt or a solvate.

The expression “effective amount” and “effective dose” generally denotean amount sufficient to produce therapeutically desirable results,wherein the exact nature of the result varies depending on the specificdisorder which is treated. When the disorder is a tumor such as cancer,the result is usually an inhibition or suppression of the proliferationof the cancer or tumor cells, a reduction of cancerous cells or theamelioration of symptoms related to the cancer cells.

The effective amount of the platinum(IV) complex of the presentinvention may depend on the species, body weight, age and individualconditions of the subject and can be determined by standard proceduressuch as with cell cultures or experimental animals. A concentration ofthe platinum(IV) complex may, for example, be at least about 10 nm.

Preferably, the IC₅₀ of the platinum(IV) complex towards tumor cellssuch as cancer cells is at most 1000 nM, in particular it is less than500 nM and further preferred less than 200 nM and most preferably lessthan 200 nM after about 72 h in particular towards cancer cells from oneof an ovarian cancer, a lung cancer, a breast cancer, or a colorectalcancer including cisplatin resistant cancer. The Resistant Factor of theplatinum(IV) complex of the present invention towardscisplatin-resistant cancer cells is preferably less than 10, morepreferably less than 8 and in particular even less than 5. The ResistantFactor is calculated by dividing the IC₅₀ of the platinum complextowards cisplatin-resistant cells by its IC₅₀ towards cancer cells ofthe same cell type or tissue which do not have a cisplatin-resistantphenotype.

The platinum(IV) complex can be present in solid, semisolid or liquidform. The platinum(IV) complex of the present invention can beadministered by an oral or parenteral route to the subject, inparticular by an oral route or an intravenous route.

The platinum(IV) complex may be administered in form of a pharmaceuticalcomposition comprising the platinum complex and a pharmaceuticallytolerable excipient such as selected from a pharmaceutically tolerablecarrier, salt, buffer, water, diluent, a filler, a binder, adisintegrant, a lubricant, a coloring agent, a surfactant or apreservative or a combination thereof. A person of skill in the art isable to select suitable pharmaceutically tolerable excipients dependingon the form of the pharmaceutical composition and is aware of methodsfor manufacturing pharmaceutical compositions as well as able to selecta suitable method for preparing the pharmaceutical composition dependingon the kind of pharmaceutically tolerable excipients and the form of thepharmaceutical composition. The pharmaceutical composition can bepresent in solid, semisolid or liquid form to be administered by an oralor parenteral route to the subject.

In an embodiment, the platinum(IV) complex can be used as a singlecompound for treating the subjects in particular with cancer.

In other embodiments, the platinum(IV) complex is administered incombination with other therapeutically effective treatments such as oneor more of:

-   -   other therapeutically effective compounds such as        chemotherapeutic compounds including, for example, a        topoisomerase-II inhibitor, an anthracycline, a coordination        complex of platinum, a taxane, a protein kinase inhibitor, a        vinca alkaloid or derivative thereof, a topoisomerase-I        inhibitor and a nucleotide analog or precursor analog;    -   radiation therapy;    -   hormonal therapy; and/or    -   targeted therapy including immunotherapy such as monoclonal        antibody therapy.

The present invention further provides a pharmaceutical compositioncomprising:

(i) a platinum(IV) complex of the present invention; and

(ii) a pharmaceutically tolerable excipient such as selected from apharmaceutically tolerable carrier, salt, buffer, water, diluent, afiller, a binder, a disintegrant, a lubricant, a coloring agent, asurfactant or a preservative or a combination thereof.

The pharmaceutical composition can be present in solid, semisolid orliquid form to be administered by an oral or parenteral route to asubject. “Pharmaceutically tolerable excipients” are those which can betaken by the subject without therapeutically relevant adverse effectsand do not negatively influence the efficiency of the platinum complex.

According to the invention is also the platinum(IV) complex describedabove, in particular of Formula (IIa), for use as a medicament for thetreatment of cancer. The platinum(IV) complex such as of Formula (IIa)can be used in an effective amount for treating an animal or a human, inparticular mammal, preferably a human. Another aspect of the inventionrefers to the use of the platinum(IV) complex described above inparticular of Formula (IIa) for preparing a medicament for treatment ofcancer. The platinum(IV) complex described above in particular ofFormula (IIa) may be used in combination with at least a furtherchemotherapeutic compound.

In another aspect, the invention provides a method for inhibiting thegrowth of tumor cells. Said method comprises the step of contacting apopulation of tumor cells such as a population of cancer cells with theplatinum(IV) complex described above which can, for example, be a saltor solvate. Preferably, the cell growth is reduced and/or cell death isinduced. MTT assay can be used for confirming the effect on cell deathand cell viability.

For example, inhibiting the growth of tumor cells can mean a decrease inthe cell viability in particular a significant decrease and/or anincrease in the number of apoptotic cells, in particular a significantincrease. The skilled person is aware of methods for verifying sucheffects such as with cell viability measurement by means of a MTSproliferation assay, a MTT assay or by determination of the apoptosisrate by means of Annexin V flow cytometry measurement. As used herein,the term “significant” means that is statistically significant asdetermined by Student's t-test or other art-accepted measures ofstatistical significance.

In particular, the platinum(IV) complex administered can comprise astructure selected from:

Most preferably, the platinum(IV) complex comprises a structure ofFormula (II), in particular of Formula (IIa):

The cells can, for example, but not limited to be from one of:

-   -   an ovarian cancer,    -   a lung cancer,    -   a breast cancer, or    -   a colorectal cancer.

The cancer cells can have a natural or an acquired resistance againstone or more chemotherapeutic compounds, in particular a natural or anacquired resistance against known coordination complexes of platinumsuch as cisplatin. Preferably, the IC₅₀ of the platinum complex towardsthe cancer cells is less than 500 nM and further preferred less than 200nM and most preferably less than 200 nM after about 72 h in particulartowards one of an ovarian cancer, a lung cancer, a breast cancer, or acolorectal cancer including cisplatin-resistant cancers. The ResistantFactor of the platinum(IV) complex of the present invention towardscisplatin-resistant cancer cells is preferably less than 8 and inparticular even less than 5.

The step of contacting the tumor cells with the platinum(IV) complex ofthe present invention may be carried out by applying an incubationsolution comprising the platinum(IV) complex to said cells whichincubation solution may further comprise suitable excipients such asbuffers or a suitable growth medium. Alternatively, contacting the tumorcells with the platinum(IV) complex of the present invention can becarried out by administering the platinum(IV) complex to a subject suchas a mammal like a human, for example, by an oral or parenteral route inform of a pharmaceutical composition as described above.

EXAMPLES

Several highly cytotoxic platinum(IV) complexes of the present inventionhave been prepared and spectroscopically characterized. The anticancereffect of the complexes has been tested with different types of humancancer cells.

Example 1A

Preparation of platinum(IV) complexes of the present inventionPlatinum(IV) complexes of the present invention were prepared byreacting c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] or [Pt(DACH)(OH)₂(ox)](DACH=trans-(1R,2R)-1,2-cyclohexanediamine, ox=oxalato) with theNHS-ester of the corresponding aryl-comprising moiety at differentreaction conditions. All reactions described herein were carried outunder protection of Argon unless otherwise noted. Agents and solventswere used as received without further drying or purification withoutfurther notification.

Platinum contents were tested by an inductively coupled plasma-opticalemission spectrometer (ICP-OES, Optima 2100DV, PerkinElmer, USA).Elemental analysis was performed on a vario micro elemental analyzer.¹H, ¹³C, and ¹⁹⁵Pt NMR spectra were measured by a Bruker Ultrashield™300, 400, or 600 MHz NMR spectrometer at ambient temperature. All NMRchemical shifts (δ) are reported in parts per million (ppm) andreferenced as described below. ¹H and ¹³C NMR spectra were referencedinternally to residual solvent peaks using deuterated dimethyl sulfoxide(DMSO-d6), or deuterated chloroform (CDCl₃) as the solvents. ¹⁹⁵Pt NMRspectrum was referenced by using external standards of K₂PtCl₄ in D₂O(δ=−1628 ppm).

Synthesis of the Platinum(IV) Complex Having Formula (IIa) (FurtherReferenced as “monochalcoPt(IV) or “Monochalcoplatin””)

Synthesis of the respective NHS ester (referred to as “chalconeNHS-ester”): Chalcone (675.0 mg, 1.92 mmol),1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) (265.7 mg, 2.31mmol), and N-hydroxysuccinimide (NHS) (442.3 mg, 2.31 mmol) were stirredin 70 mL acetonitrile at r.t. overnight. The white suspension wascollected by filtration. EDC/NHS was removed by washing with H₂O. Whitepowder was obtained after freeze drying. Pale powder. 550.0 mg, yield64.0%.

Synthesis of monochalcoPt(IV) from the chalcone NHS-ester:c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] (245.8 mg, 0.74 mmol) was suspended in 10 mLDMSO. 20 mL DMSO solution of the chalcone NHS-ester (330.0 mg, 0.74mmol) was added slowly to the stirred suspension. The reaction mixturewas stirred vigorously at r.t. for 72 h. The unreactedc,c,t-[Pt(NH₃)₂Cl₂(OH)₂] was removed by filtration, then a large amountof dichloromethane (DCM) was added to the bright yellow solution to getlight yellow precipitate. After 48 h, the precipitate was collected byfiltration and washed with DCM (5 mL×3). Yellow powder. 256.0 mg, 51.0%.¹H NMR (400 MHz, DMSO-d6) δppm 8.41 (s, 1H), 8.12 (d, J=8.4 Hz, 1H),7.93-7.71 (m, 5H), 7.01 (d, J=8.4 Hz, 2H), 6.22-5.74 (m, 6H, NH3), 4.62(s, 2H), 1.18 (s, 1H, OH). ¹³C NMR (100 MHz, DMSO-d6) δppm 186.8, 175.2,160.7, 145.3, 138.0, 135.8, 131.9, 131.1, 131.0, 130.3, 128.5, 127.2,118.7, 115.2, 65.8. ¹⁹⁵Pt NMR (129 MHz, DMSO-d6): δppm 1050. MS (ESI+)m/z: MS (ESI−) m/z: [M-H]⁻ calculated for C₁₇H₁₇N₂O₅Cl₄Pt: 664.95,found: 664.95. Anal. Calcd for C₁₉H₂₆Cl₄N₂O₇PtS: C, 29.90; H, 3.43; N,3.67. Found: C, 30.24, H, 3.98, N, 4.04.

FIG. 1 summarizes the synthesis route of monochalcoPt(IV) wherein (2) is4-formylphenoxyacetic acid (“4-formylphenoxyacetic”); i: 50% KOHsolution, r.t., 12 h; ii: diluted HCl solution, r.t., 6 h. Pale powder,80.0%.

Synthesis of the Platinum(IV) Complex Having Formula (IIb) (FurtherReferenced as dichalco-oxaliPt(IV))

1.0 equivalent [Pt(DACH)(OH)₂(ox)] (50 mg, 0.12 mmol) and 10.0equivalent chalcone NHS-ester of (519.6 mg, 1.2 mmol) were suspended in10 mL DMSO. The reaction mixture was stirred vigorously at 75-85° C. for24 h. The unreacted [Pt(DACH)(OH)₂(ox)] was removed by filtration, thena large amount of dichloromethane (DCM) and diethyl ether was added tothe bright yellow solution to get light yellow precipitate. After 48 h,the precipitate was collected by filtration and washed with DCM (5mL×3). Light yellow powder was obtained in a reasonable yield. 20.2 mg,15.7%. ¹H NMR (400 MHz, DMSO-d6) δ 8.40 (s, 1H), 8.40-8.34 (m, 1H), 8.11(d, J=8.4 Hz, 1H), 8.02-7.65 (m, 6H), 6.97 (d, J=8.0 Hz, 2H), 4.79 (s,2H), 2.08-2.05 (m, 1H), 1.48-1.40 (m, 2H), 1.11-1.05 (m, 1H).

FIG. 2 summarizes the synthesis route of dichalco-oxaliPt(IV).

Synthesis of the Platinum(IV) Complex Having Formula (IIIa) (FurtherReferenced as “mono4FP-Pt(IV)”)

Synthesis of 4-formylphenoxyacetic (4FP acid) NHS-ester:4-formylphenoxyacetic (500 mg, 2.76 mmol),1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) (638.4 mg, 3.33mmol), and N-hydroxysuccinimide (NHS) (383.3 mg, 3.33 mmol) were stirredin 70 mL acetonitrile at r.t. overnight. The white suspension wascollected by filtration. EDC/NHS was removed by washing with H₂O. Whitepowder. 630.0 mg, 82.0%. ¹H NMR (400 MHz, DMSO-d6) δ 9.91 (s, 1H),7.95-7.85 (d, J=8.0, 2H), 7.26-7.18 (d, J=8.0, 2H), 5.51 (s, 2H), 2.84(s, 4H).

Synthesis of mono4FP-Pt(IV) from the 4FP acid NHS-ester:c,c,t-[Pt(NH₃)₂Cl₂(OH)₂](100.0 mg, 0.3 mmol) was suspended in 5 mL DMSO.NHS ester of 4FP acid (83.0 mg, 0.3 mmol) was dissolved in 10 mL DMSOand was added dropwise. The reaction mixture was stirred vigorously atr.t. for 72 h or more. The unreacted c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] wasremoved by filtration, then a large amount of dichloromethane (DCM) anddiethyl ether was added to the bright yellow solution to get lightyellow precipitate. After 48 h, the precipitate was collected byfiltration and washed with DCM (5 mL×3). Yellow powder. 70.0 mg, yield47.0%. ¹H NMR (400 MHz, DMSO-d6) δ 9.87 (s, 1H), 7.82 (d, J=8.0 Hz, 2H),7.11 (d, J=8.0 Hz, 2H), 6.23-5.74 (m, 6H), 4.66 (s, 2H), 1.18 (s, 1H).

FIG. 3 summarizes the synthesis route of mono4FP-Pt(IV).

Synthesis of the Platinum(IV) Complex Having Formula (IIIb) (FurtherReferenced as “di4FP-Pt(IV)”)

c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] (100.0 mg, 0.3 mmol) and the NHS ester of 4FPacid (833.3 mg, 3.0 mmol) were suspended in 10 mL DMSO. The reactionmixture was stirred vigorously at 75-85° C. for 24 h or more. Theunreacted c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] was removed by filtration, then alarge amount of dichloromethane (DCM) and diethyl ether was added to thebright yellow solution to get light yellow precipitate. After 48 h, theprecipitate was collected by filtration and washed with DCM (5 mL×3).140.0 mg, yield 70.8%. ¹H NMR (400 MHz, DMSO-d6) δ 9.88 (s, 1H), 7.83(d, J=8.4 Hz, 2H), 7.13 (d, J=8.0 Hz, 2H), 6.85-6.32 (m, 3H), 4.80 (s,2H). Yellow powder.

FIG. 4 summarizes the synthesis route of di4FP-Pt(IV).

Synthesis of the Platinum(IV) Complex Having Formula (IIIc) (FurtherReferenced as “mono4FP-oxaliPt(IV)”)

[Pt(DACH)(OH)₂(ox)] (50.0 mg, 0.12 mmol) was suspended in 5 mL DMSO. NHSester of 4FP acid (32.2 mg, 0.12 mmol) was dissolved in 10 mL DMSO andwas added dropwise.

The reaction mixture was stirred vigorously at r.t. for 72 h or more.The unreacted [Pt(DACH)(OH)₂(ox)] was removed by filtration, then alarge amount of dichloromethane (DCM) and diethyl ether was added to thebright yellow solution to get light yellow precipitate. After 48 h, theprecipitate was collected by filtration and washed with DCM (5 mL×3).Yellow powder, 15.0 mg, 21.8%. ¹H NMR (400 MHz, DMSO-d6) δ 9.86 (s, 1H),8.20-7.87 (m, 3H), 7.82 (d, J=8.0 Hz, 2H), 7.16-7.11 (m, 1H), 7.04 (d,J=8.30 Hz, 2H), 4.72 (s, 2H), 2.65 (s, 1H), 2.46-2.44 (m, 2H), 2.04 (t,J=14.5 Hz, 2H), 1.55-0.90 (m, 6H). ¹³C NMR (100 MHz, DMSO-d6) δ 191.8,176.0, 164.2, 163.4, 132.1, 130.2, 115.5, 66.6, 61.8, 60.6, 40.9, 31.3,31.1, 24.1, 24.0.

FIG. 5 summarizes the synthesis route of mono4FP-oxaliPt(IV).

Example 1B

Cytotoxicity Analysis of the platinum(IV) complexes of the presentinvention

Cell Lines and Cell Culture Conditions

Human ovarian carcinoma A2780 and cisplatin-resistant A2780cisR cellswere cultured in RPMI 1640 with 10% FBS and 100 unitspenicillin/streptomycin. Human breast adenocarcinoma MCF-7, humancolorectal carcinoma HCT116, human lung carcinoma A549, andcisplatin-resistant A549cisR cells were cultured in DMEM containing 10%FBS and 100 units penicillin/streptomycin. Human fetal lung fibroblastMRC-5 cells were cultured in MEM with 10% FBS, 1% L-glutamine, 1%non-essential amino acids, and 1% sodium pyruvate. Cisplatin-resistantcells, A549cisR and A2780cisR, were generated from their parental A549or A2780 cells. Briefly, A549 or A2780 cells were cultured in completemedium containing 0.5 μg/mL cisplatin at the beginning for the firstscreening, and the remaining cells were cultured in complete mediumcontaining 1.0 μg/mL cisplatin for at least 4 weeks until the resistancewas obtained. All cells were incubated at 37° C. in 5% CO₂.

Cytotoxicity Test

An MTT assay was used to evaluate the cytotoxicity of cisplatin (cDDP),the platinum(IV) complex of the present invention of Formula (IIa)(monochalcoPt(IV)), chalcoplatin and cDDP combined with one equivalentligand chalcone against A2780, A2780cisR, A549, A549cisR, MFC-7 andMRC-5 cells.

For each of these assays, cells were seeded in 96-well plates at acertain density. For instance, A2780 cells were seeded in a 96-wellplate at the density of 1,500 cells per well and incubated till theconfluence reached about 30%. Cells were then treated with mediumcontaining varying concentrations of compounds for 72 h at 37° C. in 5%CO₂. DMF was used to increase the solubility of compounds, and the finalconcentration of DMF was 1% (V/V). For MTT assay, after incubation for72 h, the medium containing compounds was replaced by FBS-free mediumwith 1 mg/mL MTT for 4 h incubation. DMSO was added to each well whenthe medium containing MTT was removed after incubation. The absorbancewas measured at 570 and 630 nm. Cells incubated with medium containing1% DMF only were used as controls. The seeded cell density for A549,MCF-7 and HCT116 was 1,500 cells/well, and for A2780cisR, A549cisR, andMRC-5 was 2,500 cells were seeded to each well. The absorbance wastested at 570 and 630 nm.

The results of this assay are presented in Table 1 depicting theresulting cytotoxicity of monochalcoPt(IV) compared to the cytotoxicityof cDDP, chalcoplatin and cDDP combined with a chalcone ligand. The IC₅₀values represent the concentration of the tested compound required toinhibit cell growth by 50% compared to controls run in the absence ofadded complexes, measured by the MTT assay following a 72 h exposure.Values are the average of the 96-wells for each tested compound, and thereported errors are the corresponding standard deviations. In Table 1the FI (fold increase) is defined as IC₅₀(cDDP)/IC₅₀(monochalcoPt(IV)),and the RF (resistant factor) is defined as the respective IC₅₀ of atested compound in A2780cisR/IC50 in A2780 cells, or IC₅₀ inA549cisR/IC₅₀ in A549 cells.

As seen in Table 1, monochalcoPt(IV) is significantly more active thanboth cisplatin (cDDP) and chalcoplatin, and the IC₅₀ values ofmonochalcoplatin are in the nanomolar range in all the cells tested. Forexample, the IC₅₀ values of chalcoplatin in A2780 and A549 cells are 830and 1900 nM, respectively, while those of monochalcoPt(IV) are as low as10 nM and 80 nM, respectively. Compared with cisplatin, monochalcoPt(IV)displays up to a 422-fold increase in cytotoxicity in the cells tested.Furthermore, monochalcoPt(IV) is able to overcome cisplatin resistance.MonochalcoPt(IV) displays nanomolar cytotoxicity in both A2780cisR andA549cisR cells. In A549 and A549cisR cells, the RF value is 4.3 forcisplatin, and the value decreases to 1.8 for monochalcoPt(IV). Asimilar trend is also found in A2780 and A2780cisR cells.MonochalcoPt(IV) is also very active against the proliferation of MCF-7and HCT116 cells, and the FI value for HCT116 cells is as high as 421.9.MRC-5, the human lung fibroblast cell line, was used to evaluate thecytotoxicity of monochalcoPt(IV) against normal cells.

TABLE 1 Cytotoxicity of monochalcoPt(IV) compared to cisplatin (cDDP),cDDP with a chalcone ligand and chalcoplatin upon 72 h drug treatment incancer cells by MTT assay (IC₅₀ in nM) cDDP + Cell line cDDP Chalconechalcone chalcoplatin monochalcoPt(IV) FI^(b) A2780  830 ± 270 >35000 490 ± 320  830 ± 570 10 ± 3 83 A2780cisR 13050 ± 2300 >35000 >2000 1590± 250  70 ± 10 186 RF^(a) 16 — — 1.9 7.0 — A549 1380 ± 160 >40000  580 ±100 1900 ± 700  80 ± 10 17.3 A549cisR 5880 ± 420 >40000 6860 ± 650 1600± 500 140 ± 10 42 RF 4.3 — 12 0.84 1.8 — MCF-7 18020 ± 400  >50000 14060± 500   4800 ± 1000 240 ± 8  75.1 HCT116 9703 ± 793 N.D. 8580 ± 653 1766± 141 23 ± 6 421.9 MRC-5 4900 ± 200 65100 ± 9000 3090 ± 460 9000 ± 400110 ± 30 44.5 ^(a)RF (Resistant Factor) is defined as IC₅₀ inA2780CisR/IC₅₀ in A2780 cells or as IC₅₀ in A549cisR/IC₅₀ in A549 cells^(b)FI (fold increase) is defined as IC₅₀(cDDP)/IC₅₀(monochalcoPt(IV))

1. A platinum(IV) complex comprising a structure of Formula (I):

wherein: X, X′, Y, Y′ and Z are independently selected from an electrondonor ligand and may be linked to each other in any combination; n isselected from zero, any positive charge or any negative charge; R is anaryl-comprising moiety selected from the group consisting of:

with L and L′ being a linker group, W being a linker atom, W′ being anatom or group which can be attached by a double bond; R₁ to R₄ beingindependently selected from a substituent or a hydrogen atom and R₅being a hydrogen atom; and with the provision that the platinum complexis not chalcoplatin.
 2. The platinum(IV) complex of claim 1, wherein: X,X′, Y, Y′ and Z are independently selected from a nitrogen-containingligand, an oxygen-containing ligand, a phosphorous-containing ligand, asulfur-containing ligand and a halogen containing ligand; L is—(CH₂)_(m)— with m being an integer which is >0; W and W′ areindependently selected from a heteroatom.
 3. The platinum(IV) complex ofclaim 1, wherein: X, X′, Y and Y′ are independently selected fromammine, aqua, a halido, hydroxido, oxalato or diamines and Z is selectedfrom ammine, aqua, a halido, hydroxido, oxalato or diamines or —OR withR being as defined above; L is —(CH₂)_(m)— with m being an integerselected from 1, 2, 3 or 4; L′ is —(CH₂)_(m′)— with m′ being an integerselected from 1, 2 or 3; W is selected from an oxygen or a sulfur atom;W′ is selected from an oxygen atom or nitrogen atom; R₁ to R₄ areindependently selected from a hydrogen atom or a halogen atom and R₅ isa hydrogen atom.
 4. The platinum(IV) complex of claim 1 which comprisesa structure of Formula (III):

wherein X, X′, Y, Y′, Z, L, W, W′, n and R₁ to R₅ are as defined inclaim
 1. 5. The platinum(IV) complex of claim 1, which comprises astructure of Formula (III):

wherein: X, X′, Y and Y′ are independently selected from ammine, ahalido, oxalato or 1,2-cyclohexanediamine; Z is selected from hydroxidoor —OR with R being:

L is —(CH₂)_(m)— with m being an integer selected from 1, 2, 3 or 4; Wis selected from an oxygen atom or a sulfur atom; W′ is selected from anoxygen atom or nitrogen atom; R₁ to R₄ are independently selected from ahydrogen atom or a halogen atom and R₅ is a hydrogen atom.
 6. Theplatinum(IV) complex of claim 5, which comprises a structure of Formula(IIIa), (IIIb) or (IIIc):


7. A method for preparing the platinum(IV) complex of claim 1 by linkinga platinum(IV) complex precursor comprising a structure of Formula (XI):

with an aryl-comprising moiety R to form the platinum complex of claim1, wherein X, X′, Y, Y′ and Z are as defined in claim 1, n′ means zeroor any positive or negative charge and wherein the aryl-comprisingmoiety R is selected from one of:

wherein L, L′, W, W′ and R₁ to R₅ are as defined in claim
 1. 8. Themethod of claim 7 for preparing a platinum complex of the followingFormula (III)

the method including linking a platinum(IV) complex precursor comprisinga structure of Formula (XIa):

with X, X′, Y, Y′ and n′ as defined in claim 1, with an aryl-comprisingmoiety which is

with L, W, W′ and R₁ to R₅ as defined in claim 1, which method comprisessteps of: (i) optionally preparing a hydroxysuccinimide(NHS)-ester ofFormula (XIII):

(ii) reacting a platinum(IV) complex precursor of Formula (XIa) with theNHS-ester of Formula (XIII); (iii) isolating the platinum(IV) complex ofFormula (III).
 9. A method for treating a subject suffering from adisease comprising administering an effective amount of a platinum(IV)complex of claim 1 to said subject.
 10. The method of claim 9, whereinthe disease is a tumor.
 11. The method of claim 9, wherein the diseaseis a tumor and the subject is a human.
 12. The method of claim 11,wherein the disease is a cancer and selected from an ovarian cancer, alung cancer, a breast cancer, or a colorectal cancer.
 13. The method ofclaim 11, wherein the disease is a cancer having an intrinsic oracquired cisplatin-resistance.
 14. The method of claim 9, wherein theplatinum(IV) complex comprises a structure of Formula (III):

wherein X, X′, Y, Y′, Z, L, W, n and R₁ to R₉ are as defined in claim 1.15. The method of claim 9, wherein the platinum(IV) complex comprises astructure of Formula (IIIa), (IIIb) or (IIIc):


16. The method of claim 9, wherein the platinum(IV) complex isadministered in form of a pharmaceutical composition comprising: (i) theplatinum(IV) complex; and (ii) a pharmaceutically tolerable excipientselected from a pharmaceutically tolerable carrier, salt, buffer, water,diluent, a filler, a binder, a disintegrant, a lubricant, a coloringagent, a surfactant or a preservative or a combination thereof.
 17. Amethod of inhibiting the growth of tumor cells comprising the step ofcontacting a population of tumor cells with an effective amount of theplatinum(IV) complex of claim
 1. 18. The method of claim 17, wherein thetumor cells are cancer cells from one of an ovarian cancer, a lungcancer, a breast cancer, or a colorectal cancer.
 19. The method of claim17, wherein the tumor cells are cancer cells having an intrinsic oracquired cisplatin-resistance.
 20. The method of claim 17, wherein theplatinum(IV) complex comprises a structure of Formula (IIIa), (IIIb) or(IIIc):